In clean rooms, such as bio clean rooms, airborne microorganism particles and non-microorganism particles are detected and recorded using particle detecting devices. See, for example, Japanese Unexamined Patent Application Publication 2011-83214 and N. Hasegawa, et al., Instantaneous Bioaerosol Detection Technology and Its Application, azbil Technical Review, 2-7, Yamatake Corporation, December 2009. The state of wear of the air-conditioning equipment of the clean room can be ascertained from the result of the particle detection. Moreover, a record of particle detection within the clean room may be added as reference documentation to the products manufactured within the clean room. Optical particle detecting devices draw in air from a clean room, for example, and illuminate the drawn-in air with light. When there is a microorganism or a non-microorganism particle included within the air, a particle that is illuminated with light emits fluorescence, enabling detection of the numbers, sizes, and the like, of microorganisms and non-microorganism particles included in the air. Moreover, there is the need for technologies for accurately detecting particles in a fluid outside of clean rooms as well. See, for example, Japanese Unexamined Patent Application Publication 2013-117466.
However, when a substance that emits light in the fluorescent range but that is not a fluorescent particle that is the subject of detection is included in the fluid, such as air, that is to be inspected, then in some cases the particle detecting device may incorrectly detect this substance as a fluorescent particle that is the subject of detection. Given this, an aspect of the present invention is to provide a particle detecting device and particle detecting method able to detect accurately the fluorescent particles that are the subjects of detection.